This research will define the microvasculature of lymphatic tissues using regional perfusions with alcian blue dye to stain endothelial glycocalyx. Light and electron microscopy will describe structure of A- V shunts, high endothelial venular and venous sphincter; neuropharmacologic studies will establish regulation of these structures and their role in controlling regional blood flow. Histologic and histochemical methods will demonstrate specialized structure and metabolic activities of high endothelial venular. Phagocytic potential of this endothelium will be shown by regional infusions with particulate materials. Intercellular migration of lymphocytes through this endothelium will be proven in ultrastructural studies where hyperosmolar solutions and tracer particles delineate extracellular spaces. Membrane interactions in lymphocyte-endothelial adherence will be characterized using purified enzymes to disrupt this binding. Requirements for cell motility in emigration will be studied by determining tissue distribution of radiolabelled lymphocytes poisoned with cytochalasin B or colchamide. Similar tracer studies will determine if cellular emigration depends upon movement through a chemotactic gradient.